High frequency signal system



Aug. 14, 1934.

F, w. FRINK 1,970,424 HIGH FREQUENCY SIGNAL SYSTEM Filed.April 28, 1932 2 Sheets-Sheet l AMPL /F/E/E A PLIF/EIE J 4 AMPL/F/EES Inventor Frederic k W. Frink y fiw Q? His Attorney.

Aug. 14, 1934.

F. W. FRINK HIGH FREQUENCY SIGNAL SYSTEM Filed. April 28, 1932 2 Sheets-Sheet 2 AMPL/F/EES f AMPL/F/EES AMPL/F/EE 9 Inventor: FPedericK W. Frinh,

b WwZZ/ek,

His Attorney.

Patented Aug. 14, 1934.

PATENT OFFICE 1,970,424 I HIGH FREQUENCY SIGNAL SYSTEM Frederick W. Frink, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 28,

6 Claims.

My invention relates to high frequency signal systems and more particularly to systems of the duplex communication type.

More particularly my invention relates to signal systems in which a signal channel is rendered operative in response to the signal currents to be transmitted therethrough. In duplex communication systems, for example, it is frequently necessary to utilize the signal currents to be transmitted through either of the opposite signal channels to condition the respective channel in advance of the signal currents. It is also desirable in certain situations to utilize the currents in either channel to condition the opposite channel to prevent the transmission of currents from the particular channel through the opposite channel. Such situations arise, for example, in two-way repeater circuits where it is desired to avoid singing due to the transfer of currents from either channel to the other.

In signal systems of this type a certain time interval usually occurs between the supply of signal currents to the particular channel and the time when that channel is conditioned to transmit said currents. Similarly a time interval occurs between the supply of signal currents to a particular channel and the time when the opposite channel is conditioned to prevent trans-- mission thereof. The result is, in the first case, that the first part of the signal currents, as for example a part of the first syllable of speech, is likely to be lost in the channel before the channel is conditioned for the proper transmission thereof. This necessitates a-special design of the circuits to obtain desired quality in the received signals. In the latter case the first part of the signal currents are likely to be transmitted back through the opposite channel before that channel is rendered inoperative by the signal currents. This effect, unless special precautions are taken, is likely to cause undesired singing in the equipment.

It is desirable in systems of this type that delay or storage means he provided whereby signals supplied to either of the channels are delayed or stored for a period sufficient to permit the channel conditioning equipment to operate after which period the signals are released and transmitted through the desired channel.

One of the objects of my invention is to provide a system of the type indicated including such delay or storage equipment and which is of simple and economical construction and reliable in operation. A further object of the invention is to pro- 1932, Serial No. 607,996

vide in a system of the type indicated comprising a plurality of communication channels means whereby a single delay or storage device may be employed in common to all of the signal channels.

Still a further object of my invention is to provide a duplex communciation system in which the signals to be transmitted in either direction are stored in a common storage device for a period sufficient to permit the channel conditioning equipment to operate to condition the system for transmission of said signals after which the signals are automatically released and supplied to the properly conditioned channel.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention, however, both as to its organization and method of operation together with further objects, and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 and Fig. 3 represent different embodiments of my invention, and Fig. 2 shows in greater detail the type of delay means employed.

Referring to Fig. 1 of the drawing I have shown therein my invention as applied to a carrier current communication system, such as is, commonly employed for single frequency duplex communication over the lines of a power distribution system. The carrier current transmitter of the system shown in Fig. .1 comprises an oscillator including a three-element electron discharge device 1 having an oscillatory circuit 2 connected between its grid and cathode. ,thereby to cause the discharge device 1 to produce oscillations of a suitable frequency. These oscillations are amplified by a power amplifier 3 and supplied through a three-winding transformer 4 to the power distribution system 5. The oscillations generated by the oscillator 1 are modulated by means of signal currents received from a desired signal circuit, such as a telephone line 6, these signals being supplied to the carrier current transmitter through a channel including a transformer 7, conductors 8, audio amplifiers 9 and 10, signal storage equipment 11, audio amplifiers 12, transformer 13, au-

dio amplifier l4, and modulator 15. The modulator 15 is arranged in any suitable manner to modulate the oscillations, which are amplified by the amplifier 3, in accordance with the signal currents received from the telephone line 6.

Currents received from the power line 5 are supplied through the transformer 4 to a radio frequency receiver 16 where they are demodulated and the audio signals supplied through audio amplifiers 17, 18 and 10 to the storage equipment 11. From the output of the storage equipment 11 signals'are supplied through amplifiers 12 and transformers 13 and '7 to the telephone line 6.

It will be observed that the secondary winding of transformer 13 which is included in the output of the delay equipment is arranged to be connected by relay 19 alternately to the telephone line 6 and the input to the audio amplifier 14. Normally the relay 19 is in the position shown in which position signal currents from the telephone line are transmitted through the armature 20 of the relay 19 and its left hand contact to the amplifiers 9 and 10 and the delay equipment. From the output of the delay equipment the signals are transmitted through the amplifiers 12, transformer 13 and the armature 21 of the relay 19 to the amplifier 14 and the radio frequency transmitter. Thus normally signals are transmitted from the telephone line 6 to the input of the radio frequency transmitted.

The oscillator 1 however of the radio frequency transmitter is normally inoperative and is rendered operative only by the signal cur: rents received from the telephone line. This is effected by means of a control electron discharge device 22 which is connected in series with the anode and cathode of the discharge device 1, these devices being energized from a source of electromotive force 23. This circuit extends from the positive side of the source of electromotive force through the choke coil 24, anode and cathode of device 1, anode and cathode of device 22 and resistance 25, to the negative side of the source 23. The grid of device 22 is normally biased negatively by means of a source of electromotive force 26 to such an extent that no current flows in the anode circuit thereof, and accordingly the, oscillator 1 is rendered inoperative. Signal currents received from the telephone line 6, however, are supplied through conductors 8 and amplifiers 27 to an electron discharge apparatus 28. This apparatus may be of any suitable type whereby a relay 29 is reliably operated in response to signal currents. This apparatus may, for example, be constructed in accordance with the disclosure of my application, Serial No. 581,871, filed December 18, 1931, and entitled Carrier current thyratron circuits. Upon operation of relay 29 by means of its left hand contact it supplies a positive potential from the source 30 to the grid of the discharge device 22, thereby permitting current to flow in the anode circuit of the oscillator 1 and rendering the oscillator 1 operative to generate oscillations. By means of the right hand armature of relay 29 the receiving channel is short circuited at the output of the audio amplifier 17. Further, when current flows in the anode circuit of the oscillator 1 and control tube 22 a potential is developed upon resistance 25 which may be supplied to the grid of one of the amplifiers in the radio receiver 16, thereby to drive this grid either sufficiently negative or sufiiciently positive to render the amplifier inoperative. This is conventionally shown in the drawing by the conductors 31 extending to the rectangle 16 and terminating respectively in. a conventionally indicated cathode and grid. In this way in response to currents received from the telephone line 6 the oscillator 1 is rendered operative to transmit high frequency oscillations and at the same time the receiving channel isrendered inoperative. v

A certain time interval however elapses between the receipt of signals from the telephone line 6 and the time when the oscillator 1 has come into operation and the receiving channel has been rendered inoperative. It is desirable that the signals received from the telephone line 6 be stored in the system during this time interval and for this reason the storage device 11 is provided and normally connected between the telephone line 6 and input to. the transmitter. This device comprises a rotating disk having a few turns of hard magnetic wire wound about the periphery thereof. Adjacent this periphery is placed a recording winding 32 and a reproducing winding 33, these windings being wound upon U-shaped cores cooperating with the periphery of the disk. The recording winding is connected in the output of the amplifier 10 and the reproducing winding is connected to the input of the amplifiers 12. Between the windings 32 and 33 is placed a permanent magnet 34 which likewise cooperates with the disk and is of suflicient strength magnetically to saturate the magnetic conductor wound upon the periphery of the disk. As thus constructed it will be seen that signals received from the line 6 are supplied through conductors 8 both to the recording winding 32 and to the input to the channel conditioning equipment 27, 28, 29, 25, 31; The signals are thus magnetically stored upon the wire of the rotating disk 11 for a period sufiicient to permit the discharge device 1 to build up oscillations and the receiving channel tobe rendered inoperative. By this time or thereafter the signals recorded on the wire have been carried around by the disk to the reproducing winding 33 where they are reproduced in the winding and supplied through the amplifiers 12 and 14 to the modulator 15. The signals are then erased from the magnetic conductor by means of the permanent magnet 34.

It will be observed that normally the receiver 16 is operative. Accordingly received signals are amplified and detected in the receiver 16 and the audio signals are supplied to an audio amplifier 35 and relay control equipment 36. This latter equipment is similar to that mentioned in connection with the relay control equipment 28 and serves reliably to operate the relay 19 in response to received signals. The signals are also simultaneously supplied through the amplifiers 18 and 10 to the recording winding 32 where they are stored upon the magnetic conductor and wound upon the periphery of the disk 11 for a period suificient to permit the relay 19 to operate thereby to connect the secondary winding of transformer 13 to the telephone line. After this has been done the signals are reproduced by the winding 33 and supplied through the amplifiers 12 and transformers 13 and 7 to the telephone line.

Amplifiers 9 and 18 are included in the system at the positions indicated to prevent, by their unilateral characteristic, the transmission of signals from the telephone line to device 36 or from the-receiver 16 to device 28.

. It will be observed that as thus arranged only a single delay device is required to delay the signals in both the transmitting and receiving channels during operation of the conditioning equipment; that is, signals from the telephone line 6 and also signals from the receiver 16 are both recorded upon the disk 11 for a period sufiicient to permit the respective conditioning equipment to operate, after which time the signals are released and supplied to the corresponding signal channel.

Because of the delay produced by the storage equipment 11 any special construction of the channel control equipment for quick operation may be entirely avoided. The relays l9 and 29, for example, may be of relatively rugged construction and capable of operating a number oi armatures. Further, they may be adjusted for operation only in response to a relatively large received electromotive force thereby rendering them inoperative in response to small electromotive forces which may be induced in the corresponding signal channels through undesired inductive, capacitive, or noise, efiects. Further, it will be observed that the usual hybrid coil construction commonly employed to render the output from the receiver and the input to the transmitter conjugate with respect to the telephone line are wholly avoided. Similarly the use of a hybrid coil in the position of the transformer 4 is likewise avoided.

Fig. 2 shows the signal storing equipment in somewhat greater detail. The disk 11 may be of any suitable size and is continuously rotated by any suitable means. It will be observed that the hard steel wire which is wound upon the periphery of the disk does not terminate at the periphery but rather that the ends thereof are brought down upon the opposite sides of the disk as indicated at 3'7 the terminal portion of the conductors progressively receding from the periphery rather than terminating abruptly upon the periphery. In this way it has been found that undesired clicks produced by the abrupt termination of the wire upon the pe-.

riphery of the disk are avoided. The coils 32 and 33 are shown wound upon their respective cores cooperating with the periphery of the disk. These coils preferably are arranged at right angles to each other to avoid any direct energy transfer therebetween, whereby all the energy supplied from one coil to the other is supplied through the magnetic material mounted upon the disk. In this way the necessity for any shielding between these coils is avoided.

In Fig. 3 I have shown a further modification of my invention in which a simplification of the conditioning apparatus is also effected. In this figure the relay control apparatus corresponding to 28 and 36 of Fig. l are shown in detail, this I apparatus comprising a vapor electric device 38 which operates in response to currentsreceived from the telephone line 6 to control the relay 29, a vapor electric device 38' which responds to currents received in the radio receiver 16 to control the relay 19, and an additional vapor electric device 39 which responds to operation of either vapor electric device 38 or 38' to deenergize the corresponding relay. As is well 'known these vapor electric devices have the characteristic that they abruptly break down and pass current when the voltage on the grid exceeds a predetermined value. When broken down they continue to pass current even though this voltage be removed. Accordingly the device 39 is necessary to restore these devices to their normal condition. The anode circuits of vapor electric devices 38 and 38' are energized from a common source of unidirectionalelectromotive tween the conductors 40 and 41 and the cathode thereof is connected at a common point upon the anode circuits of devices 38 and 38 such that normally the grid of device 39 is negative with respect to the cathode thereby rendering this device non-conducting, whereas when either device 38 or 38 is conducting the cathode of device 39 becomes negative with respect to the grid thereby rendering that device conducting. The device 39 thereupon renders the corresponding device 38, 38' non-conducting.

Referring to device 38 it will be seen that the grid thereof is connected through a transformer 44 to the output of amplifier 27. This grid is biased negatively by means of the portion 45 of a potentiometer which is connected across the station bias supply mains 53. The bias supplied by the resistance 45 is sufiicient to render thedevice 38 normally non-conducting. When signals are received from amplifier 27, however,

resistance 46, and resistance 47 to the positive side 40 of the source of electromotive force. Relay 29 thus operates to short circuit the output from amplifier 17, to render the oscillator l operative and, through action of the control tube 22, resistance 25 and conductors 31, to

render the receiver 16 inoperative. The current however which flows through resistance 47 from the vapor electric device 38 is of such a value as toreduce the potential of the cathode of device 39 from that of the conductor 40 to a potential somewhat below that of the potential of the' grid of device 39 thereby rendering the device 39 conductive during the half cycles when its anode is positive. Current which flows in the anode circuit of relay 39 flows from the cathode through resistance 46 and relay 29, armature 48 of relay 29 which is now in its closed position and thence through the secondary winding of transformer 42 to the anode of device 39. The potential developed across resistance 46 and relay 29, which are included in the anode circuit of device 38, is of such a value as to reduce the voltage between the anode and cathode of device 38 to such a value that this device is no longer conducting. After this device becomes non-conducting device 39 becomes non-conducting at the end of the positive half cycle. Accordingly, devices 38 and. 39 are alternately conductive during the period when signals are received. When these currents are interrupted the device 38 is rendered non-conducting by the device 39 and the relay 29 is then deenergized. A copper oxide rectifier of any suitable type 49 is connected across relay 29 to avoid surge effects or transient voltages due to rapid decay of current in the relay winding at the tion of the system is rendered less erratic in anode of device 38, relay 19, resistance 46', and resistance 47, to the positive side 40 of the source of electromotive force. Device 39 is then rendered conductive as previously described and passes current through a circuit extending from the cathode thereof through resistor 46, winding of relay 19, armature 50 of relay 19 and secondary winding of the transformer 42 to the anode of device 39. This current develops a potential across resistance 46' and relay 19, which are included in the anode circuit of device 38', sufiicient to render device 38 nonconductivc. When device 38 becomes non-conductive device 39 likewise becomes non-conductive but the cycle repeats itself so long as signal currents are supplied to device 38' thereby maintaining relay 19 energized during the entire period when the signal currents are received.

It will be observed that with this arrangement only three vapor electric devices are employed in connection with the two channels, and further that any necessity for separate bias sources for these devices is avoided, the bias for devices 38 and 38 being supplied from the station bias supply mains 53 and the bias for device 39 being supplied from the source of anode'potential for device 38 and 38.

It will be observed that relays 29 and 19 control contacts 51 and 52 respectively which serve to reduce the negative bias on the grid of the corresponding vapor electric device 38, 38, This is advantageous since it assures that when the received signal currents are just sufiicient to cause either device 38 or 38' to break down it will continue to break down on succeeding cycles of operation of the respective device 38, 38' and 39 notwithstanding some reduction in intensity of the received signals. In this way the operacase of slight fluctuations in received signal intensity.

While I have shown particular embodiments of my invention it will of course be understood that I do not wish to be limited thereto since' many modifications both in the circuit arrangements and the instrumentalities employed may be made. I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a pair of signal channels, a delay device arranged to receive signals from both of said channels, individual means for each of said channels responsive to signals at the input to said delay device and operable during the interval of delay produced by said delay device to conditiornthe respective channel, and means common to both channels for restoring said last two means to normal condition when said signals are interrupted.

2. In combination, a signal channel, means responsive to currents in said channel to transmit current to condition the channel in advance of the signal, a second channel, means responsive to currents in said second channel to transmit current to render said first channel inoperative, and means common to both channels responsive to current transmitted by either of said last two means for restoring said last two means to normal condition when said signals are interrupted.

In combination, a signal channel, a vapor electric device, means responsive to signals in said channel to cause break down of .said vapor electric device, means responsive to current in said vapor electric device to condition the channel in advance of the signal, a second channel, a second vapor electric device, means responsive to current in said second channel to cause break down of said second device, means responsive to current in said second device to render said first channel inoperative, means including a third vapor electric device responsive to break down of either of said first mentioned vapor electric devices to restore the respective channel to normal condition after said signals are interrupted.

4. In combination, a signal channel, means responsive to currents in said channel to transmit current to condition the channel in advance of the signal, a second channel, means responsive to currents in said second channel to transmit current to render said first channel inoperative, means common to both channels responsive to current transmitted by either of said last two means for restoring said last two means to normal condition when said signals are interrupted, and means responsive to current transmitted by either of said first two means to connect said last means selectively to respond to current transmitted by the respective one of said first means.

5. In combination, a plurality of signal channels, a plurality of vapor electric devices, each of said vapor electric devices being connected to a corresponding one of said channels and adapted to break down and pass current-when signal current in the respective channel exceeds apredetermined value, means to supply unidirectional potential to the anodes of said vapor electric devices, means responsive to current flowing in the anodes of said vapor electric devices to prepare said channels for desired transmission of the signals causing fiow of said current, and a single means responsive to current in all of said plurality of vapor electric devices to render the vapor electric device broken down nonconductive, whereby each device is conductive only during the presence of signal currents in the corresponding signal channel exceeding said predetermined value;

6. In combination, a plurality of signal channels, a plurality of vapor electric devices, each of said vapor electric devices being connected to acorresponding one of .said channels and adapted to break down and pass current when signal current in the respective channel exceeds a predetermined value, means to supply unidirectional potential to the anodes of said vapor electric devices, means responsive to current flowing in the anodes of said vapor electric devices to prepare said channels for desired transmission of the signals causing flow of said current, a resistance connected in series with the anodes of all of said vapor electric devices, a plurality of additional resistances, each of said additional resistances being connected in series with the anode of a corresponding vapor electric device, and means responsive to current in i FREDERICK W. FRINK. 

